Uf, I am glad :- ). I wasn't sure if I wasn't misreading some more complex issue.
I think it comes down to knowledge of photography within 3D world, lot of people aren't aware that for example 50mm focal length exists within smaller one like 35mm, if you crop that image, and end result would be identical perspective ( this would be solution to Iker's issue for wanting something bit wider, he would change focal length, and then crop the ratio to more horizontal). I am pretty sure overscan plugin which I never used does exactly that just calculates it so you don't have to do the cropping by eye. Shift on top just allows non-symmetrical crop additionally.